Precast Concrete Sandwich Panels Research Articles

Seismic behavior of horizontally spliced single-side superposed shear wall using a concealed column

The single-side superposed (SSS) shear wall is an innovative precast concrete sandwich panel that better meets the requirements of building industrialization. However, the seismic behavior of SSS shear walls remains inadequately understood. In this paper, a full-scaled horizontally spliced SSS shear wall using a concealed column and an integral SSS shear wall of the same dimensions were tested. The seismic behavior was investigated considering various aspects including hysteresis performance, bearing capacity, ductility performance, energy dissipation capacity, and stiffness degradation curve. The simulation models were established by the Abaqus, which provided the verification and further research for the test. Furthermore, two innovative splicing forms were proposed to optimize the existing specimens through the Abaqus. The experimental results indicated that implementing the vertical joint would lead to a decrease in the yield-bearing capacity by 24%, but it would also enhance the ultimate bearing capacity by 12.7%. Meanwhile, the deformation capacity would improve by 9.7%. The numerical simulations demonstrated that the suggested splicing methods effectively meet the demands of building industrialization.

Flexural Behavior of a New Precast Insulation Mortar Sandwich Panel

This article introduces the experimental and analytical research results of two precast insulation mortar concrete sandwich panels (PIMSP) and two precast concrete composite panels as one-way slabs under bending load. Obtaining a prefabricated floor slab that can balance thermal insulation and structural performance can reduce material consumption and increase inter-story usage height. As the sandwich material for PIMSP, insulation mortar with a strength of 6 MPa was used. Truss-shaped shear connectors were used for shear force transfer. Then, finite element analysis was used to analyze and study the unidirectional flat plate model. The results showed that the tested PIMSP achieved a complete composite effect in the elastic stage and a semi-composite effect in the plastic stage. The PIMSP crack pattern resembles that of a precast concrete slab when utilized as a one-way slab. The load transfer capacity of truss-shaped shear connectors is relatively small, and it is mainly used as a connection between floors. Experiments have demonstrated that PIMSP panels can serve as a structural substitute for regular concrete floors in residential buildings.

Shear performance of X and Z configuration wythe ties for insulated precast concrete sandwich panels using different FRP materials

This study investigates Insulated Precast Concrete Sandwich Panels (PCSP), a versatile system integrating structural and thermal efficiencies suitable for diverse structures. PCSP's structural behavior depends on effective shear force transfer between two wythes through components known as "Wythe Ties." Testing twelve push-off specimens explores angled connectors with various FRP-composite Wythe Tie configurations to assess stiffness in PCSP design. Serving as the second phase of experimental work after prior findings' publication, the research compares Steel, Carbon, and Basalt FRP wythe tie behaviors, analyzing key factors' influence on strength, stiffness, and deformability. Evaluation includes performance assessments of shear strength, relative slip, stiffness, and failure modes. To validate, a nonlinear 3D-FE analysis simulates tested specimens' behavior, revealing a fitting progressive failure pattern and demonstrate good agreement with experimental results. The study unveils significant shear tie variations in PCSPs, where type and configuration impact ultimate capacity, stiffness, and toughness of wythe ties. Notably, Notably, for X-configuration shear ties, steel and CFRP-bar shear ties were observed to be the most effective material types. On the other hand, for Z-configuration shear ties, CFRP-Strip and CFRP-bar shear ties were identified as the most effective material types. Overall, these insights guide designers in choosing suitable wythe tie configurations and materials for specific PCSP applications.

Study of the flexural performance and a novel calculation formula for the degree of composite action for precast concrete sandwich panels

SummaryThis study investigates the flexural performance and degree of composite action (DCA) of precast concrete sandwich panels (PCSPs) with four types of connectors. Five full‐scale specimens were designed, and 4‐point bending tests were performed. The specimens included four PCSPs utilizing glass fiber reinforced polymer (GFRP) truss connectors, steel truss connectors, concrete rib connectors, and GFRP pin connectors, respectively, along with a solid panel (SP). The results indicated that the flexural performance and DCA provided by the four types of connectors followed an ascending order as follows: GFRP pin‐type connectors, GFRP truss connectors, steel truss connectors, and concrete rib‐type connectors. Moreover, the study presented a novel method for calculating DCA, namely, the neutral axis method, which was compared with the displacement and strain methods. The reasonableness and accuracy of the neutral axis method in calculating DCA during the linear elastic stage were verified. Results indicated that the neutral axis method provided more precise and reasonable DCA that closely matched the experimental results compared with the displacement and strain methods. Additionally, the neutral axis method was simpler to calculate DCA and had a broader range of applications. Finally, the study provided recommendations for the optimal application scenarios of each calculation method.

Experimental analysis on the out-of-plane structural performance of single-face superposed shear walls with different horizontal connections

Single-face superposed (SFS) shear wall is a novel precast concrete sandwich panel (PCSP) wall that can be used as load-bearing walls in high-rise buildings and underground structures in seismic zones. This paper investigates the out-of-plane structural performance of SFS shear walls with different horizontal connections. Three SFS shear walls with different lap-spliced rebar connection configurations at the horizontal connections were designed and tested to compare their out-of-plane structural performance with that of a cast-in-place specimen, in terms of failure modes, cracking patterns, load-displacement curves, stiffness degradation curves, ductility, and force transfer mechanism of lap-spliced rebar connections. The test results showed that the SFS shear wall specimens exhibited and maintained a high level of composite action until failure, and the studied three different horizontal connections can allow effective force transfer between the upper shear walls and the lower. The stiffness, ductility, and ultimate bearing capacities of SFS shear walls under out-of-plane monotonic loading were significantly higher than those of cast-in-place shear walls. The bearing capacity was found to depend to a large extent on the location of additional vertical connecting rebar, the displacement mainly caused by rigid body rotation and related to crack width at joint. A calculation method of the ultimate bearing capacity of a SFS shear wall under out-of-plane horizontal loads was proposed. Finally, some suggestions on the setting of the vertical connecting bar are put forward.

Flexural performance of novel ECC-RC composite sandwich panels

To address the shortcomings of precast concrete sandwich panels (PCSPs) such as insufficient load-bearing capacity, poor ductility behavior, and susceptibility to cracking under temperature stress, this study reinforced the face layer of PCSP with engineered cementitious composite (ECC), resulting in the development of novel ECC-RC composite sandwich panels (ECSPs). The flexural performance of ECSP was revealed by way of a four-point bending test and finite element analysis. Test results showed that incorporating ECC into the wythes substantially improved the flexural performance of PCSP, and the maximum crack width of ECSP was well below the corresponding limit requirement when the mid-span deformation reached the serviceability limit state of the panel. ECSP presented a long load-hardening phase owing to the excellent tensile toughness of ECC, and the properties of the reinforcement could be fully utilized in ECSP without causing “over reinforced” damage as seen in PCSP. Finite element analysis demonstrated that the initial cracks of ECSP did not occur at the tensile edge of the panel, indicating excellent durability of ECSP. Based on the test results and finite element analysis, a formula for the flexural carrying capacity of ECSP was proposed, and the corresponding calculation model demonstrated better applicability. It is recommended to use 20 mm thick ECC to reinforce the face layer of ECSP for optimal economic benefits in practical engineering, while paying attention to the interface problem between ECC and concrete.

Holistic analysis for the efficiency of the thermal mass performance of precast concrete panels in hot climate zones

PurposeThis paper investigates thermal mass performance (TMP) in hot climates. The impact of using precast concrete (PC) as a core envelope with different insulation materials has been studied. The aim is to find the effect of building mass with different weights on indoor energy consumption, specifically cooling load in hot climates.Design/methodology/approachThis research adopted a case study and simulation methods to find out the efficiency of different mass performances in hot and humid climate conditions. Different scenarios of light, moderate and heavyweight mass using PC have been developed and simulated. The impact of these scenarios on indoor cooling load has been investigated using the integrated environment solution-virtual environment (IES-VE) software.FindingsThe results showed that adopting a moderate weight mass of two PC sheets and a cavity layer in between can reduce indoor air temperature by 1.17 °C; however, this type of mass may increase the cooling demand. On the other hand, it has been proven that adopting a heavyweight mass for building envelopes and increasing the insulation material has a significant impact on reducing the cooling load. Using a PC Sandwich panel and increasing the insulation material layers for external walls and thickness by 50 mm will reduce the cooling load by 15.8%. Therefore, the heavyweight mass is more efficient compared to lightweight and moderate mass in hot, humid climate areas such as the UAE, in spite of the positive indoor TMP that can be provided by the lightweight mass in reducing the indoor air temperature in the summer season.Originality/valueThis research contributes to the thermal mass concept as one of these strategies that have recently been adopted to optimize the thermal performance of buildings and developments. Efficient TMP can have a massive impact on reducing energy consumption. However, less work has investigated TMP in hot and humid climate conditions. Furthermore, the impact of the PC on indoor thermal performance within hot climate areas has not been studied yet. The findings of this study on TMP in the summer season can be generated in all hot climate zones, and investigating the TMP in other seasons can be extended in future studies.

Shear Transfer Mechanism between CFRP Grid and EPS Rigid Foam Insulation of Precast Concrete Sandwich Panels

An experimental program was implemented to investigate the shear transfer mechanism of carbon-fiber-reinforced polymer (CFRP) grids and expanded polystyrene (EPS) rigid foam insulation in three wythe precast concrete sandwich wall panels. The purpose of the research was to measure the shear flow capacity and to observe the failure mode(s) of precast concrete sandwich panels manufactured with a CFRP grid shear transfer mechanism between wythes. Six precast concrete sandwich panels were examined by push-out tests in which the center concrete wythe was pushed downward with respect to two outer concrete wythes. It was observed that the average shear flow capacity of the specimens having 2 in (51 mm) thick foam was higher than that of the specimens having 4 in (102 mm) thick foam. In addition, stiffness decreased significantly when the thickness of the EPS insulation increased. The failure mode for the panels included relative displacement between the center concrete wythe and the outer concrete wythes. Test results showed that panels tended to fail by CFRP grid rupture, CFRP grid pull-out, and loss of bond at the concrete/foam interface. Further tests should be performed to fully comprehend the nature of the shear transfer mechanism between the specific CFRP grid used and EPS rigid foam insulation.

Shaking table tests and seismic assessment of a full-scale precast concrete sandwich wall panel structure with bolt connections

A novel, light-weight, sustainable, repairable and cost-effective precast concrete sandwich wall panel structure system is proposed in this paper, including the dry bolt connections and the precast concrete sandwich panels. To evaluate the seismic performance of precast structure system, a sequence of shaking table tests is carried on the full-scale precast concrete sandwich wall panel structure, and the dynamic characteristics, damage pattern, dynamic responses and seismic fragility are investigated and analyzed by the test results under service level earthquake, design based earthquake, and maximum considered earthquake. The seismic fragility curves and failure probability curves are analyzed by the shaking table test results, which quantitatively describes the seismic performanceexpressed by probability. The results show that the precast concrete sandwich wall panel structure performs high lateral stiffness, large safety margins and high strength reserves. The precast concrete sandwich wall panel structure system presents a good seismic performance. The damage of the structure is slight under maximum considered earthquakes, and the structure has begun to enter the plastic stage. The light-weight characteristic reduces the dynamic responses, and the mild sliding between precast components consumes a fraction of seismic energy.

Structural performance of a façade precast concrete sandwich panel enabled by a bar-type basalt fiber-reinforced polymer connector

Structural performance of a façade precast concrete sandwich panel enabled by a bar-type basalt fiber-reinforced polymer connector

Study on impact resistance of precast light-weight concrete sandwich panels

To investigate the dynamic impact resistance of precast lightweight sandwich panels (PLCSP) composed of non-sintered coal ash ceramsite concrete and self-developed thermal blocking shear connectors, drop hammer impact tests with different impact energy were carried out in the central area of the exterior wythe. The dynamic response of PLCSP under different steel fibers content, wythe thickness, and the different number of shear connectors was compared and analyzed. The numerical simulation was carried out by LS-DYNA. The results show that 2% volume fraction of steel fibers enhance the stiffness of the panel by improving the overall impact toughness, while the increase in wythe thickness slows down the panel amplitude to enhance the stiffness. The exterior wythe of the PLCSP has penetrated failure, and the failure mode of the interior wythe changes from bending failure to collapse failure with the increase of the number of shear connectors. Therefore, the arrangement spacing of shear connectors can be appropriately reduced to reduce the risk of collapse failure. The ratio of maximum displacement and residual displacement of the panel under different impact energies ranged from 3.37 to 5.94, and the maximum erosion depth of the hammer was twice the displacement of the bottom of the panel, indicating that the unique sandwich structure and material of the PLCSP have good impact resistance. The research results can provide reference for the design and application of PLCSP.

Mechanical and Thermal Properties of Composite Precast Concrete Sandwich Panels: A Review

Precast concrete sandwich panels (PCSPs) are utilized for the external cladding of structures (i.e., residential, and commercial) due to their high thermal efficiency and adequate composite action that resist applied loads. PCSPs are composed of an insulating layer with high thermal resistance that is mechanically connected to the concrete. In the recent decades, PCSPs have been a viable alternative for the fast deployment of structures due to the low fabrication and maintenance cost. Furthermore, the construction of light and thin concrete wythes that can transfer and resist shear loads has been achieved with the utilization of high-performance cementitious composites. As a result, engineers prefer PCSPs for building construction. PCSP design and use have been examined to guarantee that a building is energy efficient, has structural integrity, is sustainable, is comfortable, and is safe. Hence, this paper reviews the expanding knowledge regarding the current development of the mechanical and thermal properties of the PCSPs components; subsequently, future potential research directions are suggested.

The Shear Behavior of Insulated Precast Concrete Sandwich Panels Reinforced with BFRP

Typical insulated precast concrete sandwich panel (PCSP) systems are composed of two concrete wythes separated by a layer of insulation. The structural behavior of insulated PCSP systems heavily depends on elements between two wythes known as connectors, which ensure they work as a whole. Double shear tests were carried out on 58 insulated PCSP specimens reinforced with basalt fiber-reinforced polymer (BFRP) connectors; failure modes, load displacement curves and bearing capacity of BFRP connectors were obtained. Effects of diameter, insulation thickness, installation angle, layout spacing and combined action on shear capacity were analyzed. The results show that the span ratio of the connector was suggested to be less than 15, and the angle of the connector should be set to 60° or 75° for suitable stiffness and bearing capacity with an abundant safety margin. The shear capacity decreases slightly with the increase in the connectors’ spacing while the overall impact is small. The shear force of connectors in a plane or spatial combination can be calculated according to that of one single connector. Moreover, the shear capacity model of BFRP connectors proposed in this paper provides a favorable design option for insulated PCSP systems using BFRP connectors.

Shear behavior of stainless-steel plate connectors for insulated precast concrete sandwich panels

In this study, 24 double-shear tests were performed on precast concrete insulated sandwich panels using stainless-steel plate connectors. Parameters in the test program included connector shear directions (in-plane/out-of-plane), presence of insulation (with/without), cavity widths (30 mm/80 mm/120 mm) and connector heights (120 mm/160 mm). In order to test the pure shear capacity of connectors, the insulation was removed in the in-plane shear tests. The test results indicated that the connectors with 80 mm and 120 mm cavity width failed by shear buckling and the connectors with a cavity width of 30 mm were pulled out after buckling when subjected to in-plane shear. For the out-of-plane shear tests, bending of connectors occurred in the specimens without insulation, and connectors were pulled out in the specimens with insulation. For in-plane shear connectors with cavity widths of 30 mm, 80 mm and 120 mm, the shear capacities of 120 mm high connectors were 31.8 kN, 25.8 kN and 11.5 kN respectively, while the shear capacities of connectors with a height of 160 mm were 49.3 kN, 30.2 kN and 17.6 kN. The shear capacities of the out-of-plane connectors was only 3.7% of the in-plane connectors. It was also indicated that the presence of insulation significantly contributed to shear transfer in out-of-plane shear tests, leading to 28.6 times higher shear capacity than the specimens without insulation. Based on Basler's tension field theory, an analytical model was developed to predict the shear capacity of plate connectors. Compared with test results in this paper and other studies, the predictions were in good agreement.

Research on the out-of-plane mechanical performance of double-face superposed shear walls with different horizontal connections

The horizontal connections play a critical role in resisting gravity and lateral loads in precast concrete sandwich panel shear wall structures and it's important to fully understand their behavior under various loading conditions. This study aims to investigate the out-of-plane mechanical behavior of double-face superposed shear walls with horizontal connections featuring different lap-spliced rebar connection configurations. Three full-scale double-face superposed shear walls were tested to investigate their out-of-plane structural performance with that of a cast-in-place shear wall in terms of failure modes, cracking patterns, strain analysis, deformation analysis, load-displacement curves, and force transfer mechanism of lap-spliced rebar connections. The double-face superposed shear walls displayed and maintained a fully composite manner until failure, and the examined three different horizontal connections can allow effective force transfer between the shear walls and the main structure. The final crack distribution and failure mode of double-face superposed shear walls were almost similar to that of the cast-in-place shear wall all exhibiting obvious out-of-plane bending failure characteristics. While the initial stiffness, ultimate bearing capacity and displacement ductility capacity of double-face superposed shear walls were higher. A mathematical model predicting the ultimate bearing capacity of the double-face superposed shear wall under out-of-plane horizontal loads was proposed.

Flexural behaviour of full-scale precast recycled concrete sandwich panels with BFRP connectors

In prefabricated buildings, the exterior walls play an important role in the mechanical stability and thermal insulation of the structures. In this study, a new type of precast sandwich wall panel was developed by using recycled aggregate (RA) and basalt-fibre reinforced polymer (BFRP) shear connectors. A series of double shear tests were designed and conducted to evaluate the effect of the insertion angle of the BFRP connectors on their shear performance. Based on the test results, six full-scale precast sandwich panels, including two conventional panels with glass-fibre reinforced polymer (GFRP) needle connectors, were cast and tested under four-point bending loads. The tested parameters included the distribution of BFRP connectors and the RA content. In addition, the flexural performance of the new sandwich wall panel was compared with that of conventional non-composite panels. The results showed that the proposed precast sandwich wall panels exhibited better load bearing capacity and ductility. Smaller insertion angles of the BFRP shear connectors led to greater stiffness and better shear transfer capacity because they closely connected two concrete wythes in the sandwich panels. The new recycled concrete sandwich panel is also a more environmentally friendly alternative to conventional panels for use in the exterior walls of prefabricated buildings.

Experimental Investigation of Concrete Sandwich Walls with Glass-Fiber-Composite Connectors Exposed to Fire and Mechanical Loading

Precast concrete sandwich panels (PCSPs) are known for their good thermal, acoustic and structural properties. Severe environmental demands can be met by PCSPs due to their use of highly thermally insulating materials and non-metallic connectors. One of the main issues limiting the wider use of sandwich walls in construction is their unknown fire resistance. Furthermore, the actual behaviour of connectors and insulation in fire in terms of their mechanical performance and their impact on fire spread and the fire resistance of walls is not fully understood. This paper presents an experimental investigation on the structural and thermal behaviour of PCSPs with mineral-wool insulation and glass-fiber-reinforced polymeric bar connectors coupling two concrete wythes. Three full-size walls were tested following the REI certification test procedure for fire walls under fire and vertical eccentric and post-fire mechanical impact load. The three test configurations were adopted for the assessment of the connectors’ fire behaviour and its impact on the general fire resistance of the walls. All the specimens met the REI 120-M criteria. The connectors did not contribute to the fire’s spread and the integrity of the walls was maintained throughout the testing time. This was also confirmed in the most unfavourable test configuration, in which some of the connectors in the inner area of the wall were significantly damaged, and yet the structural connection of the concrete wythes was maintained. The walls experienced heavy heat-induced thermal bowing. The significant contribution of connectors to the stiffness of the wall during fire was observed and discussed.

Vulnerability assessment of an innovative precast concrete sandwich panel subjected to the ISO 834 fire

Development and use of preconstruction have been exhibited for several decades. Numerous modules, ranging from the simplest to the most advanced concepts, have been suggested to ameliorate the layout of building structures, with respect to a broad spectrum of needs. This study aims to unfold the fire defensiveness of an innovative precast concrete sandwich wall-system subjected to the ISO 834 fire, such as this is provided for in EN1991-1-2. In light of a rapidly evolving environment that should shield structures against fire, this investigation emphasises on the vulnerability of precast panels with a varying thickness of insulation by means of a numerical methodology and a versatile heat transfer-model. A finite-element analysis is carried out with COMSOL Multiphysics® simulation software. In a following step, as fire risk should be vigorously tackled, the research is extended to validate numerical predictions of the model by means of an experimental setup for wall specimens arranged in the laboratory. Therefore, an additional goal of this research is to assess temperature discrepancies for both addressed cases. Despite various approximations of the model, an excellent agreement between numerical and experimental results is shown, confirming the rationality of computational simulations in terms of temperatures’ precision. It has been revealed that for all examined cases, the insulation ability (I) has been maintained for more than 3 h regardless of the positioning of the insulation. Further evidence though suggested that is not the case for the loadbearing capacity (R), as the installation of a fire exposed insulation layer resulted in lower stability systems. Also, the effect of the insulation thickness is not that dominant as on average and maximum temperature deviations among marginal assemblies (dEPS = 2 cm and dEPS = 10 cm) did not exceed 5 °C and 10 °C at tfire ≈ 100 min.

Experimental and analytical investigations on the failure modes of concrete sandwich panels under axial compression

In this paper, precast lightweight Concrete Sandwich Panels (CSP) with reinforced concrete skins/wythes, truss shear connectors and expanded polystyrene core are proposed to be a good alternative for replacing conventional load bearing brick masonry walls. Literature review indicated that studies examining the failure modes of concrete sandwich panels under axial compression are not reported. Towards filling this gap and for developing design guidelines for practical applications, in this paper, failure modes of CSP are theoretically defined. Experimental investigations are conducted to determine the actual failure modes, strength and behaviour of the panels under axial compression. The failure modes observed from the experimental study are compared with the theoretical failure modes. Test results indicated that CSP can be used for practical applications as an alternative to conventional brick masonry walls. Attempts are also made to find the applicability of available strength predicting formulas of sandwich members/RC walls for concrete sandwich panels. Results showed that the available formulas have to be modified for predicting the axial compressive strength of CSP with reasonable accuracy.

Durability of GFRP connectors under sustained compression load for use in sandwich walls

Precast concrete sandwich panels are used to fulfil the rising thermal requirements. The sandwich walls consist of three layers, a facing, a thermal insulation layer, and a load bearing layer. The two outer layers are coupled by connectors made of glass-fibre reinforced polymer. A lack of knowledge about load-bearing behaviour prevents the removal of sustained compressive loads. In the context of this article, tests under sustained compressive load are presented. To represent closely the in service-conditions of sandwich walls, the examined connectors were subjected to a saturated alkaline concrete environment as well as to a specified stress level till failure occurs. Thus, the experimental setup combines alkaline resistance and creep rupture tests into one comprehensive testing. By using temperature effects as an accelerating factor, reasonable test durations were enabled. The obtained time to failure line was determined to extrapolate the characteristic values of the long-term strength for a service life up to 50 years. The test results are compared and evaluated with existing test results under a sustained tensile load.